Dwarf Forest Research Articles

Book review: Headwaters in the clouds

news and update book review Headwaters in the clouds Tropical Montane Cloud Forests, by L. A. Bruijnzeel, F. N. Scatena & L. S. Hamilton (editors), 2011, Cambridge University Press, 768 pp. £65 (Hardback) ISBN: 9780521760355; http:// www.cambridge.org/ Tropical Montane Cloud Forests (TMCFs) are gaining in scientific popularity since a first international symposium on this ecosystem was held in Puerto Rico in 1993. The promotion of the meeting by the UNESCO International Hydrological Programme illustrates a far-reaching effect of cloud forests: they act as water collectors for tropical forelands. TMCFs also harbour extraordinarily many plant species, contributing to outstanding positions in each of the five hottest spots of plant diversity. Why edit yet another comprehensive opus on TMCFs, after several previous fundamental works, despite their encompassing under 0.15% of the global terrestrial surface? The answer is clear to those who know this biome: there hardly exists a more fascinating environment than exuberant, moss-covered cloud forests, often called elfin forests due to their mystical appearance. They form highly complex ecosystems, which on different continents show divergent biocœnoses because of their fragmentation and isolated position within distinct tropical mountains in the Neotropics and, to a lesser degree, in the Paleotropics, and in a few cases even on Pacific islands. This book deals with general features of TMCFs (12 chapters) and contains examples from Middle America (21), South America (19), Southeast Asia (10), Africa (5) and Oceania / Australia (5). Most contributions result from a conference in Hawaii in 2004. A first glance reveals a nearly complete thematic spectrum. The book is subdivided into seven sections with a total of 72 chapters. The first part contains general features of TMCFs. Altitudinal distributions are presented in an introductory chapter, though integrative references to surrounding belts are missing. A useful GIS-based modelling approach provides instructive data on TMCF resources and losses including tables on their dimensions and distributions. Interestingly, Indonesia and Congo rank first in national extent, with neotropical countries falling lower down. A climate chapter is based on a dataset of 477 weather stations in cloud forest sites. Many graphs present vast dot clouds of data from stations between 200 and 5,000 m asl, which raises the confusing suspicion that TMCFs occur in regions of extremely dissimilar climates. A short but informative chapter on changes in fog precipitation should have been part of a later section, as also applies to one on epiphytism. Comments on global and local soil variations, as well as on nutrient cycling and limitation in TMCFs, provide convincing and compact estimations. Coloured maps of TMCF distribution highlight their restricted extent and natural fragmentation on a global scale. The subsequent and sadly brief section on regional aspects of floristic and faunistic diversity contains fascinating information from all TMCF- bearing continents. The range extends from research on epiphyte-diversity on solitary trees (up to 4,806 individuals of 114 vascular plant species on one single fig tree!) to potential and actual distribution patterns of the mountain tapir and Andean bear. The only point of criticism is that in a book on a biological realm this section could have been broader. The third section on hydrometeorology covers a broad remit since fog, rain and their interception are decisive triggers for the formation of TMCFs. Several parts display the importance of potential evaporation and irradiation as driving forces for the variable character of forests. Additionally, the degrees of litter mineraliation and soil acidity become crucial causes of ecological peculiarities. The contributions vary from rather specialist methodical content (e.g. measuring interception, usage of stable isotopes for diagnoses of precipitation origins) to comments on the water frontiers of biogeography 4.1, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society

Population decline of the Elfin-woods WarblerSetophaga angelaein eastern Puerto Rico

SummaryWe estimated the population density of the globally threatened Elfin-woods WarblerSetophaga angelaewithin two forest types at different elevations in the Luquillo Experimental Forest in north-eastern Puerto Rico. Population densities ranged from 0.01 to 0.02 individuals/ha in elfin woodland and 0.06–0.26 individuals/ha inpalo coloradoforest in 2006, with average rates of decline since 1989 of 0.002–0.01 and 0.003–0.06 individuals/ha respectively. These estimates show a significant general declining trend from c.0.2 individuals/ha in 1989 in elfin woodland to c.0.02/ha in 2006, and from 1 to 0.2 inpalo coloradoforest. Although variation in estimated population density depended on the statistical method used, we document and discuss possible causes of an overall population decline from 1989 to 2006, lending support to previous initiatives to reclassify the species from the IUCN Red List category of “Vulnerable” to “Endangered”.

Does day length affect winter bird distribution? Testing the role of an elusive variable.

Differences in day length may act as a critical factor in bird biology by introducing time constraints in energy acquisition during winter. Thus, differences in day length might operate as a main determinant of bird abundance along latitudinal gradients. This work examines the influence of day length on the abundance of wintering crested tits (Lophophanes cristatus) in 26 localities of Spanish juniper (Juniperus thurifera) dwarf woodlands (average height of 5 m) located along a latitudinal gradient in the Spanish highlands, while controlling for the influence of food availability, minimum night temperature, habitat structure and landscape characteristics. Top regression models in the AIC framework explained 56% of variance in bird numbers. All models incorporated day length as the variable with the highest magnitude effect. Food availability also played an important role, although only the crop of ripe juniper fruits, but not arthropods, positively affected crested tit abundance. Differences in vegetation structure across localities had also a strong positive effect (average tree height and juniper tree density). Geographical variation in night temperature had no influence on crested tit distribution, despite the low winter temperatures reached in these dwarf forests. This paper demonstrates for the first time that winter bird abundance increases with day length after controlling for the effect of other environmental variables. Winter average difference in day length was only 10.5 minutes per day along the 1°47′ latitudinal interval (190 km) included in this study. This amount of time, which reaches 13.5 h accumulated throughout the winter season, appears to be large enough to affect the long-term energy budget of small passerines during winter and to shape the distribution of winter bird abundance under restrictive environmental conditions.

Soil organic matter in density fractions as related to vegetation changes along an altitude gradient in the Wuyi Mountains, southeastern China

Density fractionation can be a useful means of separating soil organic matter (SOM) into light and heavy fractions. Our objective was to evaluate SOM storage in density fractions and the relative contribution of the light fraction to total SOM pool under four different vegetations, including evergreen broad-leaved forest (EBF), coniferous forest (CF), dwarf forest (DF) and alpine meadow (AM), along an altitude gradation in the Wuyi Mountains of southeastern China, and to investigate the factors controlling the pool size in density fractions. Here we separated light and heavy fractions using 1.7 g cm −3 sodium iodide solution. The concentrations of C and N in light and heavy fractions were the highest in AM soils, while the C/N ratios in density fractions were the highest in CF soils across soil depths. The amounts of C and N in the heavy fractions increased with increasing silt plus clay content in the corresponding soil depth. Greater SOM storages in light and heavy fractions under AM suggested that the accumulation of SOM at higher altitude (lower soil temperature and higher soil moisture) mainly depends on slower decomposition rate despite lower organic matter inputs rate. The relatively larger contribution of the light fraction to total SOM under CF than that under the other three vegetation types is mainly attributed to its higher amount and quality of litterfall input and greater fine root biomass. Significant correlation existed between light fraction C and N, dissolved organic C, microbial biomass C and N, indicating considerable cycling of C and N between these pools. A stronger correlation between heavy fraction C and microbial biomass C suggested that the heavy fraction organic matter could be associated with most microbial biomass.

Community characteristics of tropical montane evergreen forest and tropical montane dwarf forest in Bawangling National Nature Reserve on Hainan Island, South China

Community characteristics of tropical montane evergreen forest and tropical montane dwarf forest in Bawangling National Nature Reserve on Hainan Island, South China

Air temperature and soil phosphorus availability correlate with trait differences between two types of tropical cloud forests

Tropical cloud forests are characterized by lower air temperature and high frequency of fog condensation at canopy level, as compared with forests at lower altitudes. Few studies have been conducted to understand differences of plant functional traits in relation to the environment in this kind of forest. In this paper, we explored the community-level differences of specific leaf area (SLA) and height of plants in relation to major environmental conditions between two adjacent tropical cloud forests on Hainan Island, South China. We measured the two functional traits for all individual plants within twenty-nine and thirty-two 10m×10m plots located in a low altitude tropical montane evergreen forest (TMEF) and a high altitude tropical dwarf forest (TDF), respectively.The results showed that both mean SLA and height decreased from TMEF to TDF, while phenotypic plasticity for the two functional traits increased from TMEF to TDF. Correlation analysis and multiple regression analysis showed that the mean SLA and its plasticity were significantly correlated with both air temperature and soil phosphorus. The mean height was only significantly correlated with air temperature, but its plasticity was significantly correlated with both air temperature and soil phosphorus.Our results suggest that plants in dwarf tropical cloud forests have decreased SLA and height, correlated with less favorable soil and atmospheric conditions, with a higher plasticity of these traits, as compared with the tropical montane evergreen forest. Community-level differences in SLA and plant height thus can be taken as indicators characterizing plant distribution to different types of tropical cloud forests.

Effects of soil mesofauna and microclimate on nitrogen dynamics in leaf litter decomposition along an elevation gradient

The nutrient dynamics in decomposing litter has proved to play a crucial role in regulating the nutrient status of ecosystems and vegetation productivity. Little is known, however, about the effect mechanism of decomposer and its environment on the nitrogen (N) mineralisation of litter along an elevation gradient in such sites. We investigated the effects of soil mesofauna using litter bags on N dynamics in decomposing Castanopsis carlesii litter along an elevation gradient across four types of ecosystems in southeastern China: evergreen broadleaf forest (EVB), coniferous forest (COF), dwarf forest (DWF) and alpine meadow (ALM). The mean contribution of soil mesofauna to N concentration was 12.6% at EVB, 10.6% at COF, 5.4% at DWF, and 3.1% at ALM. The N concentration of litter with mesofauna was significantly related to H′ (Shannon-Wiener) and GN (group number) across the four sites. The effects of soil mesofauna on N concentration of litter were significantly linked to some special faunal groups, including Oribatida, Mesostigmata and Collembola. The N concentration in litter bags were positively related with mean annual air temperature, soil temperature and litter moisture along the elevation gradient. We concluded that the rapid accumulation of N in lower elevation sites during the first few months can result in the retention of mobile N in soils and the effects of soil mesofauna on N dynamics may be intimately associated with microclimate (warm and humid) and faunal diversity along the elevation gradient. Key words : Nitrogen concentration, mesofauna, faunal diversity, elevation gradient, Wuyi National Nature Reserve, China.

Estimating state-wide biomass carbon stocks for a REDD plan in Acre, Brazil

As in many other developing countries, the state government of Acre, Brazil, is developing a program for compensating forest holders (such as communities of rubber tappers and indigenous peoples as well as small, medium and large private land holders) reducing their emission of atmospheric heat-trapping gases by not deforesting. We describe and then apply to Acre a method for estimating carbon stocks by land cover type. We then compare the results of our simple method, which is based on vegetation mapping and ground-based samples, with other more technically demanding methods based on remote sensing. We estimated total biomass carbon stocks by multiplying the measured above-ground biomass of trees >10 cm DBH in each of 18 forest types and published estimates for non-forest areas, as determined by measurement of 44 plots throughout the state (ranging from 1 to 10 ha each), by land-cover area estimated using a geographical information system. State-wide, we estimated average above-ground biomass in forested areas to be 246 ± 90 Mg ha −1; dense forest showed highest (322 ± 20 Mg ha −1) and oligotrophic dwarf forest ( campinarana) the lowest biomass (20 ± 30 Mg ha −1). The two most widespread forest types in Acre, open canopy forests dominated by either palms and bamboo (for which ground-based data are scant), support an estimated 246 ± 44 and 224 ± 50 Mg ha −1 of above-ground biomass, respectively. We calculate the total above-ground biomass of the 163,000 km 2 State of Acre to be 3.6 ± 0.8 Pg (non-forest biomass included). This estimate is very similar to two others generated using much more technologically demanding methods, but all three methods, regardless of sophistication, suffer from lack of field data.

Tropical metacommunities along elevational gradients: effects of forest type and other environmental factors

Elevational gradients provide a natural experiment for assessing the extent to which the structure of animal metacommunities is molded by biotic and abiotic characteristics that change gradually, or is molded by aspects of plant community composition and physiognomy that change in a more discrete fashion. We used a metacommunity framework to integrate species‐specific responses to environmental gradients as an approach to detect emergent patterns at the mesoscale in the Luquillo Mountains of Puerto Rico. Elements of metacommunity structure (coherence, species turnover and range boundary clumping) formed the basis for distinguishing among random, checkerboard, Gleasonian, Clementsian, evenly spaced and nested patterns. Paired elevational transects (300–1000 m a.s.l.) were sampled at 50 m intervals to decouple underlying environmental mechanisms: a mixed forest transect reflected changes in abiotic and biotic conditions, including forest type (i.e. tabonuco, palo colorado and elfin forests), whereas another transect reflected changes in environmental conditions but not forest type, as its constituent plots were located within palm forest. Based on distributional data (presence versus absence of species), the mixed forest transect exhibited Clementsian structure, whereas the palm forest transect exhibited quasi‐Gleasonian structure. In contrast, the distribution of modes in species abundance was random with respect to the latent environmental gradient in the mixed forest transect and clumped with respect to the latent environmental gradient in the palm forest transect. Such contrasts suggest that the environmental factors affecting abundance differed in form or type from those affecting distributional boundaries. Variation among elevational strata with respect to the first axis of correspondence from reciprocal averaging was highly correlated with elevation along each transect, even though axis scores were not correlated between mixed forest and palm forest transects. This suggests that the identity of the environmental characteristics, or the form of response by the fauna to those characteristics, differed between the two elevational transects. Despite the proximity of the transects, the patchy configuration of palm forest, and the pervasive distribution of the dominant palm species, the relative importance of abiotic variables and habitat in structuring gastropod metacommunities differed between transects, which is remarkable and attests to the sensitivity of metacommunity structure to environmental variation.

Biodegradation and chemical characteristics of hot-water extractable organic matter from soils under four different vegetation types in the Wuyi Mountains, southeastern China

Water extractable organic carbon (WEOC) is the most active soil organic carbon and plays an important role in global C cycling. Our aim was to investigate the biodegradability and the chemical characteristics of hot-water extractable organic matter (HWEOM) from soils under different vegetation types, including evergreen broad-leaved forest (EBF), coniferous forest (CF), dwarf forest (DF) and alpine meadow (AM), across an altitude gradation in the Wuyi Mountains of southeastern China. We quantified the biodegradability in a 90 day incubation experiment by measuring the loss of hot-water extractable organic carbon (HWEOC) and calculated the sizes of labile and stable HWEOC pool and the respective decomposition rate constants by a double exponential model. We used UV and fluorescence spectroscopic techniques to characterize the structural properties of HWEOM and measured the contents of carbohydrates, phenols and hydrophilic carbon of HWEOM solution. The extent of HWEOC biodegradation was higher in EBF and DF soils with about 20% HWEOC loss, and the labile C accounted for 13–15% of the total HWEOC. HWEOC from CF soils was the least degradable with only 12% HWEOC loss. The estimated mean residence time of the labile HWEOC pool was 8–10 days, whereas that of the stable HWEOC pool ranged from 3 to 6 years. The biodegradability of HWEOC increased with decreasing soil C/N ratio, aromaticity and humification indices, proportion of phenols and increasing proportion of hydrophilic carbon.

Diversity and Status of Butterflies across Vegetation Types of Mt. Hamiguitan, Davao Oriental, Philippines

An inventory was conducted to determine the diversity and status of butterflies of Mt. Hamiguitan Wildlife Sanctuary, Davao Oriental, using quadrat method in five vegetation types, namely; agroecosystem (10-400 masl), dipterocarp (500-900 masl), montane (900-1400 masl), mossy (1400-1500 masl) and pygmy (1500-1675 masl). Two 20m x 20m plots were established per vegetation type. These inventory techniques revealed 142 species of butterflies plus one new subspecies described and illustrated. Diversity assessment using Shannon-Weiner index showed high level (4.1) in the Montane forest as compared to other vegetation types. Bray-Curtis similarity index showed low species similarity in pygmy, mossy and agro-montane forests (< 40 %). Furthermore, this study revealed 7 possible new species, 44 endemics: 2 eastern Mindanao endemic (very rare), 4 Mt. Hamiguitan endemic (very rare), 16 Mindanao endemic and 22 Philippine endemic. Seven species are new records in Mindanao. Mt. HamiguitanWildlife Sanctuary is the home of diverse and endemic butterfly species. Â Keywords - butterflies, species richness, pygmy vegetation types, Mt. Hamiguitan

A Complex Metacommunity Structure for Gastropods Along an Elevational Gradient

The metacommunity framework integrates species-specific responses to environmental gradients to detect emergent patterns of mesoscale organization. Abiotic characteristics (temperature, precipitation) and associated vegetation types change with elevation in a predictable fashion, providing opportunities to decouple effects of environmental gradients per se from those of biogeographical or historical origin. Moreover, expected structure is different if a metacommunity along an elevational gradient is molded by idiosyncratic responses to abiotic variables (expectation=Gleasonian structure) than if such a metacommunity is molded by strong habitat preferences or specializations (expectation=Clementsian structure). We evaluated metacommunity structure for 13 species of gastropod from 15 sites along an elevational transect in the Luquillo Experimental Forest of Puerto Rico. Analyses were conducted separately for the primary axis and for the secondary axis of correspondence extracted via reciprocal averaging. The metacommunity exhibited quasi-Clementsian structure along the primary axis, which represented a gradient of gastropod species specialization that was unassociated with elevation. The secondary axis represented environmental variation associated with elevation. Along this axis, the metacommunity exhibited Clementsian structure, with specialists characterizing each of three suites of sites that corresponded to three distinct forest types. These forest types are associated with low (tabonuco forest), mid- (palo colorado forest), or high (elfin forest) elevations. Thus, variation among sites in species composition reflected two independent processes: the first decoupled from elevational variation and its environmental correlates, and the second highly associated with environmental variation correlated with elevation.

Habitat Identification for Three California Species ofSanfilippodytesFranciscolo (Coleoptera: Dytiscidae)

Three species of the genus Sanfilippodytes Franciscolo, 1979 (Sanfilippodytes adelardi [Rochette, 1983], Sanfilippodytes bidessoides [Leech, 1941], and Sanfilippodytes setifer Roughley and Larson, 2000) have been described from ponds or rain pools in the town of Caspar, California. These species were found to be strongly associated with the pygmy forest of Mendocino, California. The soils of the pygmy forest are strongly podsolized and nearly impenetrable to water. As a result, rain water pools and quickly becomes acidified. All three species were found in these acidic pools, where they are often quite abundant. The small number of specimens collected prior to this study was most likely a result of having an inadequate understanding of the habitat.

Spectroscopic characterization of hot-water extractable organic matter from soils under four different vegetation types along an elevation gradient in the Wuyi Mountains

Water extractable organic carbon (WEOC) is the most active component in global carbon cycle and its chemical and structural characteristics most likely influence its biodegradation. Our objective was to investigate the structural characteristics of hot-water extractable organic matter (HWEOM) from soils collected at various depths (S1, S2, S3) under four different vegetation types, i.e. evergreen broad-leaved forest (EBF), coniferous forest (CF), dwarf forest (DF) and alpine meadow (AM) along an elevation gradient in the Wuyi Mountains, and to relate its structural characteristics to soil properties and biological properties. Here we examine the structural characteristics of HWEOM by UV, fluorescence and Fourier-transform infrared (FTIR) spectroscopic techniques. In the synchronous fluorescence spectra of all HWEOM samples, the main emission peaks were aromatic amino acid-like fluorophores, fulvic acid-like fluorophores and polycyclic aromatic structures with a high degree of conjugation. FTIR spectroscopy showed that HWEOM featured aliphatic C–H, aromatic C=C and carbohydrate C–O functional groups. The aromaticity, the humification indices (HIXem, HIXsyn) and the fluorescence efficiency of HWEOM from the S1 layer were significantly higher in CF than those in the other three vegetation types and, in all cases they decreased with depth in the soil profile. Soil C/N ratio was highly correlated with UV absorption, humification indices and fluorescence efficiency of HWEOM. Soil metabolic quotient (qCO 2) was highly negatively correlated with UV absorption and humification indices of HWEOM. The ratio of microbial biomass C to total organic C was significantly correlated with humification indices and fluorescence efficiency of HWEOM. Our results indicate that the HWEOM from CF soils contain more highly condensed aromatic and/or heterocyclic compounds and, at the same time, the high molecular weight and complex molecules are less mobile, leading to being preferentially retained in the upper soil layer.

Effects of microclimate, litter type, and mesh size on leaf litter decomposition along an elevation gradient in the Wuyi Mountains, China

AbstractLitter decomposition is an important ecosystem process regulated by both biotic factors (e.g., decomposers and litter types) and abiotic factors (e.g., temperature and moisture). This study examined the regulatory effects of soil fauna and microclimate on decomposition of two substrates (Castanopsis carlesiiandPinus taiwanensis) along an elevation gradient in four ecosystems of zonal vegetation types in southeastern China: evergreen broadleaf forest (EVB), coniferous forest (COF), dwarf forest (DWF), and alpine meadow (ALM). Our objective was to identify the mechanisms by which microclimate, substrate, and fauna control litter decomposition, especially where variations in ecosystem structure and environment are markedly shown across an elevation gradient. The hypotheses were as follows: (1) litter decomposition within the same litter type would decrease across the elevation gradient, (2) litter decomposition would be lower in poorer nutrient quality substrate across the four sites, and (3) litter dynamics, influenced by strong interactions among ecosystem type, litter type, and decomposers, would vary by elevation gradient due to microclimate effects (i.e., temperature and moisture). The decomposition rates ofC.carlesiiwere significantly higher than those ofP.taiwanensisat EVB, COF, and DWF sites; however, they were not significantly different at the ALM site. Low elevation forests possessed a microclimate (warm and humid) that favors decomposer activities and also appeared to possess a decomposer community adapted to consuming large amounts of leaf litter, as indicated by the rapid leaf litter loss. Litter decomposition in micro‐mesh bags proceeded more slowly compared to litter in meso‐mesh and macro‐mesh litterbags across the elevation gradient, indicating that restricting some detritivore access to litter reduced litter mass loss. We suggest that microclimate and faunal contributions to plant litter decomposition differ markedly across the ecosystems in the Wuyi Mountains.

Persistence with Chytridiomycosis Does Not Assure Survival of Direct-developing Frogs

The chytrid fungus, Batrachochytrium dendrobatidis (Bd) has been linked to extinction and decline of numerous amphibians. We studied the population-level effects of Bd in two post-decline anuran species, Eleutherodactylus coqui and E. portoricensis, at El Yunque National Forest, Puerto Rico. Data on amphibian abundance was updated to report long-term population trends. Mark-recapture data was used to monitor Bd-infection status and estimate survival probabilities of infected versus uninfected adults. Prevalence of Bd (number of infected/total sampled) and individual infection level (number of zoospores) were compared among age classes at Palo Colorado Forest (661 m) and Elfin Forest (850 m). Results revealed that both species continued to decrease in Palo Colorado Forest, while in the Elfin Forest, E. portoricensis recuperated from drastic declines. Age class, season, and locality significantly predicted zoospore load. Age was also significantly associated with high zoospores loads among Bd-positive frogs, and the prevalence of Bd was higher in juveniles than adults in all populations studied. We suggest that early age represents a critical life stage in the survival of direct-developing frogs infected by this fungus. Survival probability was always higher for uninfected frogs, but recapture rates of infected versus uninfected adults were significantly different only in Palo Colorado, alerting that the negative effect of Bd infection under enzootic conditions is greater at mid-elevations. This work contributes to our understanding of how direct-developing amphibians persist with Bd, pointing to critical life stages and synergistic interactions that may induce fluctuations and/or declines in the wild.

Biophysical controls on accretion and elevation change in Caribbean mangrove ecosystems

Habitat stability of coastal ecosystems, such as marshes and mangroves, depends on maintenance of soil elevations relative to sea level. Many such systems are characterized by limited mineral sedimentation and/or rapid subsidence and are consequently dependent upon accumulation of organic matter to maintain elevations. However, little field information exists regarding the contribution of specific biological processes to vertical accretion and elevation change. This study used biogenic mangrove systems in carbonate settings in Belize (BZ) and southwest Florida (FL) to examine biophysical controls on elevation change. Rates of elevation change, vertical accretion, benthic mat formation, and belowground root accumulation were measured in fringe, basin, scrub, and dwarf forest types plus a restored forest. Elevation change rates (mm yr − 1) measured with Surface Elevation Tables varied widely: BZ-Dwarf (−3.7), BZ-Scrub (−1.1), FL-Fringe (0.6), FL-Basin (2.1), BZ-Fringe (4.1), and FL-Restored (9.9). Root mass accumulation varied across sites (82–739 g m −2 yr −1) and was positively correlated with elevation change. Root volumetric contribution to vertical change (mm yr − 1) was lowest in BZ-Dwarf (1.2) and FL-Fringe (2.4), intermediate in FL-Basin (4.1) and BZ-Scrub (4.3), and highest in BZ-Fringe (8.8) and FL-Restored (11.8) sites. Surface growth of turf-forming algae, microbial mats, or accumulation of leaf litter and detritus also made significant contributions to vertical accretion. Turf algal mats in fringe and scrub forests accreted faster (2.7 mm yr −1) than leaf litter mats in basin forests (1.9 mm yr −1), but similarly to microbial mats in dwarf forests (2.1 mm yr −1). Surface accretion of mineral material accounted for only 0.2–3.3% of total vertical change. Those sites with high root contributions and/or rapid growth of living mats exhibited an elevation surplus (+2 to +8 mm yr −1), whereas those with low root inputs and low (or non-living) mat accumulation showed an elevation deficit (−1 to −5.7 mm yr −1). This study indicates that biotic processes of root production and benthic mat formation are important controls on accretion and elevation change in mangrove ecosystems common to the Caribbean Region. Quantification of specific biological controls on elevation provides better insight into how sustainability of such systems might be influenced by global (e.g., climate, atmospheric CO 2) and local (e.g., nutrients, disturbance) factors affecting organic matter accumulation, in addition to relative sea-level rise.

Complex spatial structure in a population of Didymopanax pittieri, a tree of wind-exposed lower montane rain forest

Didymopanax pittieri is a common shade-intolerant tree colonizing treefall gaps in the elfin forests on windswept ridgecrests in the lower montane rain forests of the Cordillera de Tilaran, Costa Rica. All D. pittieri taller than >0.5 m in a 5.2-ha elfin forested portion of a gridded study watershed in the Monteverde Cloud Forest Preserve were located, mapped, and measured. This local population of D. pittieri is spatially inhomogeneous, in that density increases with increasing wind exposure; D. pittieri are more abundant near ridge crests than lower on windward slopes. The important and ubiquitous phenomenon of spatial inhomogeneity in population density is addressed and corrected for in spatial analyses by the application of the inhomogeneous version of Ripley’s K. The spatial patterns of four size classes of D. pittieri ( 20 cm dbh) were investigated. Within the large-scale trend in density driven by wind exposure, D. pittieri saplings are clumped at the scale of treefall gaps and at the scale of patches of aggregated gaps. D. pittieri 5–10 cm dbh are randomly distributed, apparently due to competitive thinning of sapling clumps during the early stages of gap-phase regeneration. D. pittieri larger than 10 cm dbh are overdispersed at a scale larger than that of patches of gaps. Natural disturbance can influence the distribution of shade intolerant tree populations at several different spatial scales, and can have discordant effects at different life history stages.

Structural variability and species diversity of a dwarf Caribbean dry forest

Low stature woody vegetation of the south-west coast of Puerto Rico grows on a rocky calcareous substrate where plants can only root in holes, cracks, and crevices accumulating water and sediments that allow seed germination and seedling development. Being in a coastal location these communities are influenced by steady onshore winds, high solar radiation, and salt spray. We studied dwarfed forest communities located at the southern limit of the Guánica State Forest, Puerto Rico, that have a well known floristic composition, but with little information on their organization and heterogeneity. We quantified the species composition of vegetation plots located along the southern coastline and compared their structure and diversity with those of dry forests on neighboring hills. The hypothesis was that forest structural development was negatively associated with proximity to the coast line and altitude above sea level. Species richness of the coastal dwarf forest area was similar to that of inland semi deciduous forest plots with which it shares at least 15 woody species. In addition, it contains a number of species resistant to salt spray and possibly brackish water, such asConocarpus erectus, Strumpfia maritima, and Coccoloba uvifera. The average canopy height of the coastal vegetation increases from 0.4 to 2.3 m between 0 to 150 m from the coastline and 7 to 19 m elevation above sea level. Within this spatial range the predominant bearing of the canopy changes from a SE-NW direction to a SW-NE direction revealing the influence of onshore winds in combination with salt spray. The dominant woody species occur as multistemmed individuals, a characteristic probably associated to occasional heavy winds and recurrent drought that impairs shoot apical dominance. Floristic and structure comparisons with mature forest plots located between 25 and 150 m altitude showed that the coastal dwarf vegetation has a more even species dominance distribution associated with the discontinuity of substrate available for establishment.

The páramo vegetation of Ramal de Guaramacal, Trujillo State, Venezuela 1. Zonal communities

Zonal paramo vegetation communities present on top of Ramal de Guaramacal, Trujillo state, Venezuela, have been studied with the aim to provide a syntaxonomic scheme or classification, based oil analysis of the physiognomy, floristic composition, ecological relations and spatial distribution of the different vegetation communities. A total of 91 vascular species, 33 species of bryophytes and 11 species of lichens have been documented from fifty 10 m-line intercept transects, each surveying 10 in of altitudinal interval oil zonal paramo vegetation present between 2800 and 3100m altitude. The interpretation of the TWINSPAN clustering allowed the recognition of five vegetation communities at association level grouped into two alliances and one order. Three associations of lower subparamo or shrubby paramo and two of upper subparamo or bunchgrass paramo dominated by rosettes and tussock plants have been documented. The alliance Hyperico paramitanum-Hesperomeletion obtusifoliae groups the shrubby paramo associations: Ruilopezio paltonioides-Neurolepidetum glomeratae and Disterigmo acuminatum-Arcytophylletum nitidum, present on wind protected slopes, dwarf forests edges or along streams. The alliance Hyperico cardonae-Xyridion acutifoliae groups one widely distributed shrubby parama, association Cortaderio hapalotrichae-Hypericetum juniperium and two open grass paramo associations: Puyo aristeguietae-Ruilopezietum lopez-palacii and Rhynchosporo gollmeri-Ruilopezietum jabonensis, present on wind exposed slopes. Asteraceae and Ericaceae are the most speciose of families, followed by Poaceae and Cyperaceae. The most diverse genera are Ruilopezia (Asteraceae), Rhynchospora (Cyperaceae) and Hypericum (Clusiaceae). Diversity of species and growth forms is greater among the shrubby communities, decreasing in the bunch grass-rosette communities. Canonical correspondence analysis (CCA) indicates that floristic composition of zonal vegetation communities is mostly related to slope angle and altitude than to other observed variables such as pH, soil depth and humus depth. The generic and species composition is that of a rain bamboo paramo.